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May

13

Last time we talked about two questions to help you understand if you’re doing Kanban to improve your workflow, or simply keeping your tasks visible on a board. I mentioned in that post that your workflow should be more than just “not started – in progress – done” didn’t go in to why. Let’s take a look at that.

Kanban is intended to help your work go faster, by helping you tune and optimize your workflow, pointing out where the bottleneck is. Central to the operation of a Kanban system is the theory of constraints, which points out that a) every system has a bottleneck or constraint that governs how much work the overall system can do and b) trying to change your workflow anywhere other than the bottleneck is waste, because that’s not where the bottleneck is. Put simply, you need to find the bottleneck and optimize there in order to make the overall system go faster. That’s what Kanban is designed to do.

Kanban finds the bottleneck by mapping out and visualizing the workflow, and in part by setting work in progress (WIP) limits on each step, restricting the number of work items that can be in any step in the flow. Since Kanban originally came from manufacturing, we can picture this WIP limit by example: we only allow two cars to be in the section of assembly where we put on the doors. In software terms, we may restrict the number of work items that can be in the “code and unit test” step to be equal to the number of people on the team, because we don’t want team members working on more than one work item at a time.

The first rule of Kanban is “visualize your workflow,” which is achieved by making the visual Kanban board. If your workflow on the board is only “not started – in progress – done” yes, you have a visual workflow, but it’s really insufficient to do the job you hired Kanban to do. You want to find the bottleneck, but where is the bottleneck in this workflow? It’s always in the same place, “in progress.” Without a more detailed workflow you can’t see where the bottleneck is, and you only have a single WIP limit which you can adjust.

What do you do if your tasks are so different that the workflow is nearly unique per work item? In that case, I don’t know that Kanban is the best tool for you. I’ve worked with teams in this situation and you can make some progress by listening for work items that are stuck or “blocked,” but you can’t visually see them, and you can’t tune your WIP to help point them out either. Kanban is really better suited to repetitive tasks, where your workflow can be more specific than just “we’re working on it,” and you can tune your WIP limits more effectively.